Unit 2 Test Review - Genetics Flashcards
What does DNA stand for? What does it contain
-deoxyribonucleic acid
-contains the genetic information of a cell
What does DNA look like?
-double helix (ladder twisted in a clockwise direction)
What is DNA composed of? What are the four chemicals in DNA?
-deoxyribose sugars and phosphates groups (sides) and a nitrogenous base
-the four chemicals in DNA are adenine, thymine, cytosine, and guanine
What is the most basic unit of a DNA molecule? What is it made up of?
-a nucleotide
-a sugar, a phosphate group, and one of four nitrogenous bases
What is the definition of a gene? What do genes make?
-a portion/tiny section of DNA, which contains specific information which codes for particular proteins/traits
-genes make up chromosomes
-basic unit of heredity
What is chromatin?
-fibres of DNA in its uncondensed form (found in the nucleus in this specific form)
What is a chromosome?
-a structure in the nucleus that contains DNA on which a gene occupies a specific location
What two kinds of cells are multicellular organisms made out of?
-Somatic (body) cells
-Reproductive (sex cells)
What are Somatic cells?
-two sets, or the diploid (2n) number of chromosomes
-all organisms have a certain amount of chromosomes in their body cells
(human somatic cells have 46 chromosomes meaning 23 pairs called homologous chromosomes)
What are homologous chromosomes?
-similar in size and shape, and they code for the same trait. Each parent contributes one chromosome to a homologous pair.
What are sex cells(gametes)?
-contain a single set (haploid number n) of chromosomes
-gametes do not have homologous chromosomes, instead, they have one chromosome from each pair
-in the case of human gametes, we have 23 pairs of chromosomes altogether including the gametes
What are the three parts of the cell cycle, and what do they do?
1) interphase
2) mitosis (nuclear division)
3) cytokinesis (cell division)
What is interphase? (1)
-most of the cell life cycle is spent here
-there are three phases:
1) G1, cell growth and differentiation
2) S, synthesis and each chromosome is duplicated
3) G2, cell growth
What is mitosis? (2)
-nuclear division, divides the nucleus
-mother cell divides into two identical daughter cells
-mitosis ensures genetic continuity as the same genetic information is stored in the nucleus
What is cytokinesis? (3)
-cell division, a cell divides the cytoplasm into two new daughter cells
What is meiosis?
-cell division that produces gametes with the number of chromosomes from the original cell reduced by half through separation of homologous chromosomes (occurs in sex organs only)
When does meiosis begin to occur in humans?
males (xy): begins at puberty (age 9-19)
females (xx): all eggs are produced before birth and at puberty the eggs mature
Why is meiosis important?
-consists of two specialized cells known as gametes forming a zygote
-since meiosis reduces the chromosomal content by half and thus the union of the sex cells restores the diploid number and maintains the viability of the organism (if this didn’t happen, the zygote would have twice as much genetic information as needed)
What is a zygote cell?
-fertilized egg
What is fertilization?
-egg and sperm uniting
What is an embryo?
-organism in early stages of development
What are unique events in meiosis?
-homologous chromosomes pair up before division
-these homologous chromosomes look alike, code for the same traits, and one is from each parent
What is crossing over, and what’s its significance?
-occurring during prophase I, the homologous chromosomes pair up in tetrads in a process called synapsis and have certain overlapping sections that break off and switch and exchange genetic material
-they separate in the 2nd division of meiosis completely, and this is significant as it indicates genetic variation in the gametes, this is a reason why siblings look different from one another
What are alleles?
-alternate forms of genes controlling a given characteristic, found at the loci’s on homologous chromosomes
What is a Punnett square?
-a chart used to show the possible gene combinations of alleles between the two gametes of two individuals
What is a genotype?
-the actual gene makeup of an individual
What is a phenotype?
-the specific physical characteristic, dependent on the genotype and its interaction with the environment
What does homozygous mean?
-the alleles for a characteristic code are the same (two dom alleles, or two recessive)
What does heterozygous mean?
-the alleles for a characteristic code for a different trait (gene pair with dominant allele or recessive allele)
What is dominant vs recessive?
-the dominant is the allele expressed in the present heterozygous form
-the recessive is the trait expressed in the homozygous form and the one masked in the heterozygous form
What is the normal chromosomal count in humans?
-22 pairs of autosomal chromosomes (homologous)
-1 pair of sex cells (gametes)